Lock for fluid pressure actuator



Jan. 8, 1963 E. JOHNSON LocK FoR FLUID PRESSURE AcTUAToR' 2 Sheets-Sheet 1 Filed July 5. 1961 2 Sheets-Sheet 2 Jan. 8, 1963 E. JOHNSON LOCK FOR FLUID PRESSURE ACTUATOR Filed July 5, 1961 e@ ww ma www www .X

United States Patent 3,072,105 LOCK FOR FLUID PRESSURE ACTUATOR Ernest Johnson, Stanton, Calif., assignor, by mestre assignments, to Lionel-Pacific, Inc., Los Angeles, Callf., a corporation of Delaware Filed July 5, 1961, Ser. N 122,034 14 Claims. (Cl. 121-40) This invention relates to extensible and retractable actuators of the hydraulic ram or jack type for applying operating force and movement to mechanisms, and more particularly, -relates to improved means for automatically locking the piston or piston rods of such actuators against retrograde movement at the end of their travels in the cylinder until positively released by action of the actuating uid pressure applied for movement in an opposite direction.

Heretofore, numerous actuator devices of the extensible and retractable ram or jack type have been known and used which, in general, combine with a cylinder and a lluid pressure actuated piston or plunger therein, some kind of lock or latch mechanism, sometimes actuated by the applied operating fluid pressure, adapted to engage the piston or piston rod at the limit of its travel in the cylinder to lock it mechanically against reverse movement until positively driven in reverse by the operating fluid.

However, in most such locking or latching devices heretofore known, when the operating uid pressure is applied to the -actuator cylinder, a substantial force is thereby immediately built up which acts against the piston or plunger in advance of its release which results momentarily in a relatively heavy loading which must be borne by the latch mechanism just prior to and during its release. 'Ihis effect is undesirable because it serves no useful purpose in the operation of the actuator and imposes design conditions upon such latcbing mechanisms which are difiicult to meet. For example, for certain applications of the actuator device, under the before-described conditions, the latching mechanism must be either im practicably large and heavy in order to have the required strength, durability, and reliability to withstand the initial loading imposed on it prior to its release, or it will be susceptible to excessive wear or even complete failure of the latching mechanism to function.

It is, therefore, an object of this invention to provide, in connection with a fluid actuated ram or jack type actuator device employing a cylinder and a uid pressure actuated piston or piston rod therein, a locking mechanism which automatically locks the piston or piston rod positively against movement at the end of its travel, and which under the influence of operating fluid pressure applied for movement of the piston or rod in the opposite direction, automatically unlocks and releases such piston or piston -rod for such movement prior to the build-up by the uid pressure of substantial force against the piston or piston rod.

Itis a further object of this invention to provide a piston or piston rod latching mechanism which, while normally keeping the piston or piston rod positively locked against movement in its cylinder, responds to the pressure of the operating fluid applied to the cylinder first to free the piston or piston rod for movement therein in response -to such fluid pressure, prior to the occurrence of any movement thereof which would result in application of forces to the lock mechanism.

It is a still further object of this invention to provide a locking mechanism for the aforesaid purpose which has improved strength and operating characteristics.

The objects are attained in accordance with the broadest aspects of the present invention by an actuator em- 3,072,105 Patented Jan. s, 1963 rice 2 ploying a cylinder and an operating piston and piston rod assembly reciprocable in such cylinder which permits limited free axial movement of such piston relative to the piston rod upon application of operating uid pressure thereto, such limited axial movement of the piston relative to the piston rod in response to applied fluid pressure in one direction serving to actuate a locking mechanism to lock the piston rod against retrograde movement at the end of its travel, and movement of the piston relative to the piston rod in response to applied duid pressure in an opposite direction serving to actuate the locking mechanism to unlock the piston rod for return movement in the cylinder. Thus, no preloading of the lock mechanism can occur by reason of fluid pressure applied against the piston because the piston is always free of opposition to movement and transfers no moving force to the piston rod until after the locking mechanism is released.

These and other objects, advantages and features of novelty will be evident hereinafter.

In the accompanying drawings, wherein, in connection with the following description, the best mode and preferred embodiment presently contemplated by the inventor for carrying out the invention is illustrated:

FIGURE 1 is a side view, partly in longitudinal section and partly in elevation, of a uid pressure operated actuator device, embodying the present invention;

FIGURE 2 is a cross-sectional view taken on line 2-2 of FIGURE 1; l

FIGURE 3 is a fragmentary longitudinal sectional view of a portion of the apparatus of FIGURE 1, illustrating the action of the locking mechanism as the piston approaches one end of its travel;

FIGURE 4 is a side view, partly in longitudinal section and partly in elevation, of a modified form of the fluid operated actuator device of the present invention;

FIGURE 5 is a cross-sectional view taken on line 5-5 of FIGURE 4; and

FIGURE 6 is a fragmentary longitudinal sectional view of a portion of the apparatus of FIGURE 4, illustrating the action of the. locking mechanism as the piston approaches one end of its travel.

Referring first primarily to FIGURES 1, 2 and 3, wherein similar reference characters designate the same or similar parts throughout the several views, 10 is the cylinder of a fluid pressure operated actuator within which there extends an axially reciprocable piston rod 12 carrying adjacent its inner end within the cylinder 10 an axially reciprocable piston. assembly indicated generally at 14.l The elements of the piston assembly 14 are carried adjacent the inner end .of the-.piston .rodin such manner as #to have freedom for limited axial sliding movement relative to the .piston rod, as will be described hereinafter.

The head end of the cylinder 10 is closed by a cylinder head 16-which is held in sealing engagement with the end of the cylinder by an annular nut 18 threaded to the end of the cylinder at 10. The cylinder head 16 is provided with an integral end connector lug 20 containing a bearing 22, by means of which the cylinder 10 may be pivotally supported by any structure or mechanical element relative to which movement of some other mechanical element is desired. The piston rod end of the cylinder 10 is similarly closed by an annular closure member 24 threaded at 25 to the end of the cylinder 10. The bore of the closure member 24 through which the piston rod 12 slidably enters the cylinder 10 is provided with a suitable sealing gland assembly which includes an inner O ring seal 26, an intermediate felt ring 28, and an outer scraper ring 30. The-scraper ring 30 is retained by an annular retainer ring 31 which is fastened to the outer end of the closure member 24 by means of 3 a plurality of screws 32. The piston rod 12 may be provided with the usual type of rod end connector, not shown, for connection to other mechanical element to be moved relative to the actuator cylinder 10. The cylinder is provided, adjacent opposite ends thereof, with threaded ports 34 and 36 to which suitable piping connections may be made for the introduction into, or the discharge from opposite ends of the cylinder, of pressure fluid for powering the actuator.

The inner end of the piston rod 12 upon which the before-mentioned piston assembly 14 is carried is formed with a short section 38 of increased diameter, and extending inwardly thereof is an integral section 40 of reduced diameter, the juncture of such sections 38 and 40 of the piston rod forming an inwardly-facing annular shoulder 39. The piston rod 12 has a bore 42 which is provided adjacent the inner extension end thereof with internal threads 43 into which is threaded a stop nut 44 having an integral anged portion 45 forming an outwardly-facing annular shoulder 46, positioned coaxially opposite the aforementioned inwardly-facing annular shoulder 39. Secured coaxially on the extension se-tion 4 0 of the piston rod 1-2 between the aforesaid oppositely facing shoulders 39 and 46 is a piston supporting and retaining assembly comprising a pair of annular latch lianges 48 and 50 positioned in abutment with the annular shoulders 39 and 46 respectively, next adjacent thereto, aA pair of coaxial spacer sleevesSl and 52, and intermediate the spacer sleeves 51 and 52, an intermediate piston-supporting sleeve 53 of. reduced outside diameter relative to the spacer sleeves.

Thebefore-mentioned piston assembly 14,. which is carried -on the Ybefore-describedwpiston supporting as-.

sembly, is made up of a number of coaxially arranged, axially slidable annular elements comprising a centrally located, annular, lioating piston 54, a pair of intermediate channel sectioned connector rings 56 and 57, and a pair of outer, oppositely positioned end lock-ring members 58 and 59. The central, floating piston.54 is slidable axially on the sleeve 56 between end limits formed byy the oppositely, inwardly-facing shoulders 62 and 64 formed at the inner-.ends of spacer sleeves 51 and 52, respectively, and is provided with inner and outer O' ring seals 60 and 61 which make sliding, fluid sealing engagement respectively with the outer cylindrical surface of lthe sleeve 56 and the vinner cylindrical surface of the cylinder 10. Coupled with. and longitudinallyI slidable together with the floating piston 54 are the before-mentioned connector rings 56 and 57, and these connector rings are constructed in split or segmental form, not shown,- so. that they may be readily coupled at 66 and 68 with the piston 54 to be moved longitudinal-'- ly therewith as a unit.

The outer, inwardly-hanged encl` portions. 70 andv 72 of the connector rings 56 and 57 make longitudinally slidable, lost motion, coupling engagement with outwardly-facing annular grooves 74 and 76. of the lockring members 58 and 59, respectively. Eachof the annular lock-ring members 58 and. 59 are provided-with oppositely, axially extending annular lock rings, as shown at 78 and 80, adapted to make encircling, locking engagement with' the head ends of locking lingers as hereinafter more fully described.

The two oppositely located lock-ring members 58 and 59 are urged axially outward in opposite directions toward limiting abutment with the inner-facing, annular surfaces of the latch anges 48 and 50, respectively, and at the same time, the central, oating piston 54 is normally urged into a central location, as shown in FIGURE'l, by a pair of coil springs 86 and 88 acting oppositely under compression. Thus, in operation as hereinafter described, the lioating piston 54 and lock-ring members 58 and 59 are each, within limits, independently slidable axiallyrelative to each'` other and relative to the piston rod.

Retained in opposite ends of the cylinder 10 are a plu rality of longitudinally directed, circumferentially spaced apart spring latching lingers and 91 connected inte grally at their root ends with ring members 92 and 94 respectively, which ring members are in turn retaine` in annular grooves 96 and 98 formed in the ends o cylinder 10, under the annular nut 18 and annular clc sure member 24, respectively. The outer end of eacl spring latch linger is provided with a radially inwardl` extending, endwise chamfered head, as shown at 96 an 98, adapted to make latching engagement with the an nular, charnfered grooves and 97, respectively, formel between outer beads 99 and 100 on the peripheries o the latch llanges 48 and 50, and the outer axially-facin annular surfaces of the lock-ring members 58 and S9.

The operation of the apparatus of FIGURES l, 2 am 3 is as follows:

Starting first with the piston rod 12 and piston assemblj 14 in the positions shown in FIGURE 1, wherein the pis ton rod 12 is in the extreme right-hand end of its strok in the cylinder 10, it will be seen that the heads 98 o the spring latch lingers 91 are positioned in engagemen with the annular groove formed behind the bead 104 extending around the periphery of the latch flange Sti and the heads of these fingers are locked in such posi tion by the superposed lock rim 80 of the lock rin; member 58, the lock, rim ,80 thus preventing radiallj outward escape of the heads 98 from the` groove whicl otherwise would occur by outward llexing of the. linger 91. In this latter condition, the piston rod 12 is me chanically locked against axial movement relative to th` cylinder 10, which might otherwise resultfrom externa forces Yapplied to the piston rod.

To move the piston rod 12 from the beforedescribei locked position, fluid pressure is introduced through por 36 to the right-hand end of the cylinder 10, and at thi same time, the lluid pressure in the left-hand end of thi cylinder 10 is reduced or released through port 34, re sulting in a pressure differential between the lluid pres sure in the right-hand and left-hand ends of the cylinder tendingto force the piston assembly 14 to move to thi left in the cylinder 10. However, before this dieren tial pressure can result in any force being applied fron the piston to the piston rod 12 or to any of the latchin; lingers 81, such differential pressure lirst acts on th central floating piston 54, causing it to slide to the lel on sleeve 53 against the compressive force of the coi spring 86 until it is stopped by abutment with the an nular shoulder 62 of the spacer sleeve 51. This axia motion of the piston 54 is transmitted throughthe con nector ring 57 to the lock-ring member 59, resulting il withdrawal of the lock rim 80- thereof from encirclemen of the tops of the heads 98 of the locking fingers 91 thereby freeing the heads 98 and the locking lingers t llex outwardly.

The fluid pressure differential then being elective o: the piston 54 after moving it into abutment with the an nular shoulder 62 then urges the piston rod and th piston assembly axially toward the left in the cylinder as viewed in FIGURE 1. The initial resultant left hand motion. of the piston supporting assembly includ ing the latch llange 50, by reason of the chamfer on th bead of the latch llange and the corresponding cham fer on the heads 9S of the lingers 91 causes the heads ti cam radially outwardly, out of the groove 97. The latc lingers 91 are thus caused automatically to release th piston and piston rod for axial movement from the in itial position shown in FIGURE l toward the left in th cylinder whenever tluid pressure is introduced throng port 36, and released through port 34.

When the piston rod 12"-and piston assembly 14 i: moving toward the left from the position shown in FIG URE 1 reaches the position shown in FIGURE 3, th chamfered outer end surface of the bead 99 of the locls ing liange 48 rst encounters the outer ends of the head 96 of the latching fingers 90, causing these ngers to be cammed radially outwardly, and thereby causing the outer ends of the heads 96 to move outwardly into position whereby the end edge of the locking rim 78 of the locking ring 58 is brought into endwise abutment therewith, as shown in FIGURE 3. Continued left-hand movement of the piston rod and piston assembly then results in the locking-ring member 58 and rim 78 being held stationary by the locking lingers while the latch flange 48 continues to move in a left-hand direction a distance sufficient to permit the heads 96 of the latch iingers 90 to drop into the annular groove 95 formed between the chamfered bead 99 and the adjacent annular surface of the lock-ring member 58, after which the lock-ring member 58 acting under the force of the coil spring 86 is restored to position in abutment with the annular shoulder 82 of the latch liange 48, thereby bringing the lock rim 78 into a position encircling and locking the heads 96 of the latching fingers 90 in the groove 95, thus lirmly locking the piston supporting as` sembly and piston rod against any retrograde movement to the right in the cylinder.

When it is desired to again move the piston rod in a return direction to the right in the cylinder 10, the reverse of the before-described operation is performed.

The apparatus of the alternative construction shown in FIGURES 4, 5 and 6 is as follows:

In the construction illustrated in FIGURES 4, 5 and 6, the construction is similar to that previously described in connection with FIGURES 1, 2 and 3, except mainly that a modified form of latching fingers and mechanism for actuating them is shown which has the advantages of having somewhat stronger and more reliable locking action. In this latter construction, the head end of the cylinder is closed by a cylinder head 102 which is held in fluid-tight sealing engagement with the end of the cylinder by an annular retainer nut 104, threaded to the end of the cylinder at 10. The cylinder head 102 is provided with an integral, external end connector lug containing a bearing 22 by means of which the cylinder 10 may -be pivotally supported by any supporting structure or mechanical element relative to which movement of some other mechanical element, by the actuator, is desired. The cylinder head 102 differs from that hereinbefore described in that it has a coaxially, inwardlyextending body portion 106 which terminates in a coaxial, cylindrical hub 108 of reduced diameter in which a radially outwardly facing annular groove 110 is formed. Retained circumferentially spaced-apart around the hub 108 are a plurality of longitudinally extending, circumferentially spaced-apart latching lingers 112. Each of the latching lingers 112 is formed, adjacent one end thereof, with a laterally extending hook-shaped projection as shown at 114, which is positioned such as to extend radially inwardly into the before-mentioned annular groove 1'10 and make retaining abutment with the annular shoulder :116, forming the innermost, rearwardly facing side of the annular groove 110. Each of the latching lingers 112 is also formed as a part of the before-mentioned hook-shaped projection with an end surface which slopes laterally inwardly such as to form, in elect, an endwise projection, as shown at 118, positioned to make contact with the radially extending surface of an annular retainer ring 120. 'Ihe point of such' contact between the projection 118 is radially off-set with respect to the-area of contact between the latching finger hook 114 and the abutting annular shoulder =116 whereby axial force exerted by the retainer ring 120 against the projection 118 will set up couples tending to rotate the latching lingers 112 in the direction indicated by the arrows 122.

, The retainer ring 120 is urged axially against the projection 118 of the latching lingers 112 by means of a plurality of coil springs 124 acting in compression, each of such springs being nested in longitudinal, circumfer- 6 entially spaced-apart drill holes 126 in the cylindrical body portion 106 of the cylinder head 102.

Lying in the bottom of the annular groove 110 is a split ring i128 carrying integral therewith a plurality of circumferentially spaced-apart radially outwardly-extending separator elements 130, each such separator element 130 being positioned between and serving to equally circumferentially space apart the plurality of latching lingers 112.

'I'he ends of each of the latching lingers 112 are formed, opposite the attachment ends thereof, withl radially inwardly extending latching heads 132 which are similar in shape and function to the heads 96 hereinbefore described in connection with the latching fingers 90 of FIGURE 1.

rlhe piston rod end of the cylinder 10 is provided with an end closure 24, which is similar to that describm hereinbefore in connection with FIGURE 1, which is threaded at to the rod end of cylinder 10. The closure member 24 is formed with a bore therein through which the piston rod 12 slidingly enters the cylinder and which is provided with a sealing gland assembly including an inner O ring seal 26, an intermediate felt ring 28, and an outer scraper ring 30. 'Ihe scraper ring 30, as before described, is retained by an annular retainer ring 31 which is fastened to the outer end of the closure member 24 by means of a plurality of screws 32. Retained in the piston end of the cylinder 10 by the closure 24 is a cylindrical body 134 which in all respects, internally of the cylinder, has the same shape and provisions as the hereinbefore-described body portion 106 inthe head end of the cylinder, except that, for convenience of construction, it is not made an integral part of the closure 24. This body member 134 carries a latching finger supporting hub and latching linger assembly which is identical to that hereinbefore described for the body portion 106 of the head end of the cylinder.

The piston rod 12 carries, adjacent its inner end within the cylinder 10, a piston assembly indicated generally at 14a, which is identical to the piston assembly 14 heretofore described in connccton with FIGURE 1, except for the specific form of the annular lock rims 78a and a, which serve to encircle and lock the heads 132 and 144 of the latching fingers 112 and 14b in the annular grooves a and 97a formed behind beads 136 and 138 of the annular latch flanges and 142, respectively.

The operation of the apparatus of FIGURES 4, 5 and 6 is as follows:

Starting first with the piston rod 12 and the piston assembly 14a in the position shown in FIGURE 4, wherein the piston rod 12 is at the extreme left-hand end of its travel in the cylinder 10, it will be apparent that the heads 132 of the latching fingers 112 are positioned in engagement with the annular groove 95a formed behind the chamfered bead 136, extending around the periphery of the latch ange 140, and are locked in such 'engagement by the encircling lock rim 78a of the lock-ring member 58a. The lock rim 78a thus prevents radially outward escape of the heads 132 from the groove 95a. In this latter condition, the piston rod 12 is mechanically locked against axial movement in the cylinder 10, which might otherwise result from external forces applied t0l the piston rod tending to move or displace it axially in the cylinder.

Next, to move the piston rod 12 from the beforedescribed locked position, fluid pressure may be intro right-hand ends of the cylinder, tending to move the pis-1 ton assembly 14 in a direction to the right in the cylinder 10, as viewed in FIGURE 4. However, before this differential pressure can result in any force being applied to the piston rod 12 or to any of the latching lingers 112, such differential pressure rst acts on the central floating piston 54,. causing it to slide to the right on sleeve 53 against the compressive force of the coil spring 88 until it is stopped by abutment with the annular shoulder 64 of the spacer sleeve 52. This limited motion of the piston 54 is transmitted through the lost motion connector ring 56 to the lock-ring member 58a, resulting in equal sliding motion of the lock-ring member 58a to the right, while lock-ring 59a remains in stationary abutrnent` with the annular end 84a of lock harige 142, thereby electing withdrawal of the lock rim 78a from locking encirclement of the outer surfaces of the latching heads 132 of the locking lingers 112, thereby in turn freeing the heads 132 and locking fingers 1-12 to pivot radially outward. The fluid pressure differential thereafter applied to the piston 54, after it moves into abutment with the annular shoulder 64 of the sleeve 52, urges the piston rod and the piston rod assembly carried on the inner end thereof toward the right, as viewed in FIGURE 4, and the resultant initial right-hand motion of the piston supporting assembly including the latching flange 136, causes the chamfer on the .bead 136 of the latching ange 149 to cam the heads 132 of the lingers 112 radially outward, outof latching engagement with the groove 95a formed behind the bead 136 of the latching ange 140, The latching lingers 112 are thus. caused automatically to releasethe piston and piston. rod for movement. to the right from the initial position shown in FIGURE 4; and before any force can be trans-- ferred from the piston 54 tothe piston rod and to the latching mechanism.

When Wthe pistonrod 12 and piston assembly 14a, in moving from the position shown in FIGURE 4 toward the right, reaches the position shown in FIGURE 6, the outer chamfered surface of the bead !138 of the locking ange 142 rst encounters the beveled outer ends of the heads 144 of the locking lingers 146, camming these lingers pivotally outward in the direction indicated by the arrows 147, and thereby positioning the outer ends of the heads 144 where the annular end of the locking rim 80a isbrought into endwise abutment therewith, as

shown in FIGURE 6. During further right-hand movement of the piston assembly, the locking ring member 59a and rim Sila thereon are thereby held stationary while. the latch flange 142 continues to move with the -piston rod in a right-hand direction a distance suicient to permitf the heads 144 of the latching lingers 146 to drop into the annular groove- 97a formed between the bead 138 and the adjacent annular surface of the lock ring member 59a, after which the lock ring 59a, acting under the 4force of the coil spring 88, is moved to a position in abutment with the annular shoulder 84a of the latch `lange 142, thereby extending the latch rim 80a into aposition encircling the heads 144 of the latching tingers'146, thereby locking the heads 144 in the aforesaid groove 97a and thereby restrain the piston supporting assembly and piston rod against any retrograde movement to the left in the cylinder.

Whenit is desired to again move the piston rod in a return direction to the left with respect to the beforedescribed travel in the cylinder. 10, the reverse of the before-described operation is performed.

From the before-described apparatus and mode of operation, it will be evident that a hydraulic actuator has been provided wherein the piston rod may be automatically and mechanically positively locked at either of its extreme or other predetermined positions within the cylinder. Consequently, if the piston rod has been moved to either of such positions within the cylinder and the source of Iiluid pressure supplied to the cylinder is cut ot or fails, the piston will nevertheless remain positively locked mechanically in such position. Also, although the piston is mechanically positively locked at the ends of its predetermined travel within the piston, it is auto- 8 matically unlocked whenever lluid pressure is supplied to that end of the cylinder which will urge the piston toward the opposite end'.

An important advantage of this invention is that the before-mentionedllocking and unlocking operations are accomplished in accordance with this invention at times when the locking mechanism is free from forces resulting from fluid pressure introduced into either end of the actuator cylinder for its operation. Thus, the locking mechanisms of this invention are at all times free from any forces or stresses other than those which may e imposed upon them through the piston rod from external sources such as the mechanisms to which the actuator may be attached.

While as hereinbefore mentioned in connection with the description of this invention, it may be desirable to provide means to lock the piston rod at both ends of its travel in the cylinder, it will be understood that in cer- .tain applications of the actuator, such as forV example where it is used simply as a lifting jack, only one locking mechanism need be employed in one end of the cylinder to positively hold the jack, piston and piston rod in extended or retracted position, as the case requires.

The foregoing is illustrative of the best mode and embodiment of theinvention presently contemplated, and

is not to be considered limiting. Variations maybe madeV therein by those skilled in theart, andthe invention shall include any and all such variations within the scope of the appended claims.

What is claimed is:

l. In combination: al cylinder; a piston and piston rod reciprocable axially in said cylinder, said piston being axially sldable within said cylinder .andl mounted .on. said rod with freedom for limited axialsliding movement relative thereto; means for admitting uid pressure to. an end of said cylinder to -move the piston and thereby move the rod axially in said cylinder; latching means; anchored in the' cylinder, enagageable with the rod when said rod is thus moved to a predetermined axial position` in said cylinder, to hold said rod against axial movement relative to said cylinder; annular locking means coaxially mounted on said rod with freedom for limited axial sliding movement thereon relative to said piston and rod, for. locking when in a first axial position relative to said rod, the latching means in such engagement with said rod; resilient means urging said locking means into said first position. and urging said piston into a predetermined axial positioni on said rod; and means responsive to axial sliding displacement of said piston from said predetermined position on said rod in opposition to said resilient means upon. admission of Huid pressure to the other end` of said cylinder, for moving the locking means into a second position relative to said rod effective to unlock said latch` ing means from said engagement withA the: rod, thereby,`

to release the piston and rod for axial. movement in said cylinder by said fluid pressure.

2. In combination: a cylinder; av piston rod reciprocable axially in said cylinder and a piston mounted on said rod with freedom for axial movement between fixed limits` between said locking means and said rod, biasing saidv locking means to saidrst position; and coupling means interconnecting said piston and said locking means for moving said locking means axially, in response to axial movement of, said piston in opposition to said resilient means, to a position on said rod effective -to release said interengagement, thereby to free the rod for axialmovement in said cylinder.

3. In combination: a cylinder; a piston rod reciprocable axially in said cylinder, and a piston axially slidable within said cylinder and mounted on said rod with freedom for axial movement intermediate fixed limit means thereon; resilient means urging said piston to a predetermined axial position intermediate said limit means; latching means interengageable with said cylinder and said rod when said rod is moved to a predetermined axial position in said cylinder, to hold said rod against axial movement relative to said cylinder; locking means mounted on said rod adjacent said piston with freedom for limited axial sliding movement thereon relative to said piston and rod, for locking, when in a first axial position relative to said rod and said rod is in said predetermined axial position in said cylinder, the latching means in interengagement with said cylinder and rod, and for unlocking such interengagement when in a second axial position relative to said rod; and coupling means interconnecting said piston and said locking means for moving said locking means axially on said rod, in response to axial movement of said piston and in opposition to said resilient means, to a position on said rod effective'to unlock said interengagement, thereby to free the rod for axial movement'in said cylinder.

4. In combination: a cylinder; a piston rod reciprocable axially in said cylinder; and an annular piston axially slidablewithin said cylinder' and mounted on said rod with freedom for axial movement intermediate fixed limit means thereon, said annular piston closingthe annular space between said cylinder and said rod; resilient means urging said piston to a predetermined axial position intermediate said limit means; latching means interengageable Awith said cylinder and said rod when said rod is moved to a predetermined axial position in said cylinder, to hold said rod against axial movement relative to said cylinder; annular locking means mounted coaxially on said rod adjacent said pistou with freedom for limited axial sliding movement thereon relative to said piston and rod, for locking, when in a first axial position relative to said rod and said rod is in said predetermined axial position in said cylinder, the latching means in interengagement wth said cylinder and rod, and for unlocking such interengagement when in a second axial position relative to said rod; and coupling means interconnecting said piston and said locking means for moving said locking means axially on said rod, in response to axial movement of said piston and in opposition to said resilient means, to a position on said rod effective to unlock said interengagement, thereby to free the rod for axial movement in said cylinder.

5. In combination: a cylinder; a piston rod recipocable axially in said cylinder, and an annular piston encircling said piston rod in axial sliding engagement with said cylinder and said rod, said annular piston having freedom for limited axial sliding movement on said rod; means for admitting fluid pressure to an end of said cylinder to move the piston on said rod to a limit of its freedom of movement thereon, and thereby move said rod axially in said cylinder; latching means anchored in the cylinder and engageable with means on said rod, when said rod is thus moved to a predetermined axial position in said cylinder, to hold said rod against axial movement relative to said cylinder; annular locking means coaxially encircling mounted on said piston rod with freedom for limited axial sliding movement thereon relative to said piston andl said rod for locking when in a first axial position relative to said rod,`the said latching means in such engagement with said means on the rod; resilient means urging said locking means into said first position and urging said piston into a predetermined axial position on said rod; and means responsive to axial sliding displacement of said piston on said rod in opposition to said resilient means, upon admission of fluid pressure to said end of` said cylinder, for

moving-the locking `means into a second position relative to said rod, effective to unlock said latching means from engagement with said means on said rod, thereby to release the piston and rod for axial movement in said cylinder by said fluid pressure.

6. In combination: a cylinder; a piston rod reciprocable axially in said cylinder, and an annular piston encircling said piston rod in axial sliding engagement with said cylinder and said rod, said annular piston having freedom for limited axial sliding movement on said rod; means for admitting fluid pressure to an end of said cylinder to move the piston on said rod to a limit of its freedom of movement thereon and thereby move said rod axially in said cylinder; latching means anchored in the cylinder, and engageable with means on said rod, when said rod is thus moved to a predetermined axial position in said cylinder, to hold said rod against axial movement relative to said cylinder; annular locking means coaxially encirclingly mounted on said piston rod with freedom for limited axial sliding movement thereon relative to said piston and said rod for locking, when in a first axial position relative to said piston rod, the said latching means in such engagement with said means on the rod; resilient means urging said locking means into said first position and urging said piston into a predetermined axial position ou said rod; and coaxial annular coupling means in slid- -able engagement with said cylinder interconnecting said annular locking means and said annular piston and responsive to axial sliding displacement of said piston on said rod in opposition to said resilient means, upon admission of fluid pressure to said end of said cylinder, for moving the locking means into a second position relative to said rod, effective to unlock said latching means from engagement with said means gn said rod, thereby to release the piston and rod for axial movement in said cylinder by said Huid pressure. Y I l 7. In combination: a cylinder; a piston rod reciprocable axially in said cylinder, and a piston axially slidable with# in said cylinder and mounted on said rod with freedom for axial movement intermediate a pair of fixed limit means thereon; a pair of latching means, one or the other ,of which is interengageable with said cylinder and said rod when said rod is moved to one or another of two predetermined axial positions in said cylinder; a pair of axially spaced-apart locking means mounted on said rod with freedom for axial sliding movement thereon relative to said piston and said rod between said fixed limit means, one of said locking means being positioned adjacent one end of said piston and the other of said locking means being positioned adjacent the other end of said piston; resilient means acting axially between said locking means and urging said locking means axially apart relative to one another, each normally into abutment with one of said fixed limit means for locking, when in such position, one or the other of said latching means in interengagement with said cylinder and rod; telescopic lost-motion coupling means intermediate said piston and each of said locking means effective to restrain said piston to a predetermined axial position intermediate said locking means when both said locking means are in abutment with said limit means as aforesaid, and effective to move one or the other of said locking means away from abutment with one or the other of said limit means for unlocking said latching means from such interengagement, in response to axial displacement of said piston in one or the other direction from said predetermined position; and means for admitting fluid pressure to either end of said cylinder to move said piston in either direction in said cylinder and thereby move one or the other of said locking means to unock the corresponding one of said latching means from interengagement with said cylinder and rod to free said rod for axial movement in said cylinder before forces are applied to said rod by said fluid pressure.

8. In combination: a cylinder; a piston rod reciprocable axially in said cylinder, and a piston axially slidable 1l within said cylinder and mounted on said rod with freedom for axial movement intermediate a pair of fixed limit means thereon; a pair of latching means, one or the other of which is interengageable with said cylinder and said rod when said rod is moved to one or another of two predetermined axial positions in said cylinder; a pair of axially spaced-apart locking means mounted on said rod with freedom for axial sliding movement thereon relative to said piston and said rod between said fixed limit means, one of said locking means being positioned adjacent one end of said piston and the other of said locking means being positioned adjacent the other end of said piston; resilient means acting axially between one of said locking means and said piston and between the other of said locking means and said piston and urging said locking means axially -apart relative to one another, each normally into abutment with one of said fixed limit means for locking, when in such position, one or the other of said latching means in interengagement with said cylinder and rod; telescopic lost-motion coupling means intermediate said piston and each of said locking means effective to restrain said piston to a predetermined axial position intermediate said locking means when both said locking means are in abutment with said limit means as aforesaid, and effective to move one or the other of said locking means away from abutment with one or the other of said. limit means for unlocking said latching means from such interengagement, in response to axial displacement of said piston in one or the other direction from said predetermined position; and means for admitting iiuid pressure to either end of said cylinderv to move said piston in either direction in said cylinder and thereby move one or the other of said locking means to unlock the corresponding one of said latching means for interengagement with said cylinder and rod to free said rod for axial movement in said cylinder before forces are applied to said rod by said uid pressure.

9. In combination: a cylinder; a piston rod reciprocable in said cylinder, said piston rod having axially spaced-apart limit means fixed thereon within said cylinder; an annular piston axially slidable in said cylinder and mounted axially slidable ou said rod intermediate said limit means; means for admitting fluid pressure to either end of said cylinder to move the piston and thereby move the rod axially in either direction in said cylinder; latching means anchored adjacent opposite end portions of said cylinder engageable with said rod when said rod is thus moved to opposite predetermined axial positions in said cylinder to hold said rod at either such position against axial movement relative to said cylinder; a first annular locking ring coaxially slidable on said rod between one of said limit means and one end of said piston; a second annular locking ring coaxially slidable on said rod between the other of said limit means and the other end of said piston; resilient means urging said locking ringsaxially apart and each normally into abutment with one of said stop means; coupling means interconnecting said piston independently to each of said locking rings and normally positioning said piston in a predetermined axial position on said rod intermediate said limit means when said locking rings are in abutment with said limit means, said coupling means including lost-motion means for moving the first one of said locking rings axially away from abutment with a limit means in opposition to said resilient means in response to axial displacement of said piston in one direction from said predetermined axial positon, without movement of the second one of said locking rings, upon admission of fiuid pressure to an end of said cylinder, and for moving the second one of said locking rings axially away from abutment with the other limit means in response to axial displacement of said piston in the other direction from said predetermined axial position, without movement of the first one of said locking rings, upon admission of fluid pressure to the other end of said cylinder, one or the other of said locking rings 12 being in position to lock one or the other of the latching means in such engagement with said rod when in abutment with a limit means and said rod is in one or the other of its aforesaid predetermined axial positions in said cylinder, and to unlock the latching means when moved axially away from abutment with the limit means to release the rod for axial movement in said cylinder by said fluid pressure.

l0. In a hydraulic actuator having a cylinder and a piston means reciprocable axially therein, means for locking said piston means immovable at a predetermined axial position in said cylinder, comprising: a longitudinallyextending latch finger in said cylinder having an attachment end and an opposite latching head end; means pivotally attaching said attachment end of said finger to said cylinder with freedom for limited pivotal motion in a radial plane relative to the longitudinal axis of said cylinder; resilient means biasing said finger to one limit vof said pivotal motion; a laterally extending head formed on the said latching head end of said finger; a latch recess means formed behind a laterally-extending projection carried by said piston means, said laterally-extending head and said projection being positioned for abutment upon axial movement of said piston means toward said latching finger in said cylinder and said latching head end and said projection being formed for lateral, camming engagement' with each other upon occurrence of such abutmentvl whereby upon continued axial movement of said piston meansirelative to said cylinder to" a predetermined latching position therein,- the said latching finger is pivotallycammed in opposition to said bias to slide over said projection and then be' oppositely, pivotally moved by' said bias into latching engagement within said' latch recess.-`

11. In a hydraulic'actuator'havng a'cylinder anda pistonmeans reciprocable axially therein, means for locking said piston means immovable at a predetermined axial position in said' cylinder, comprising: a longitudinallyextending latch finger in said cylinder having an attach'- ment end portion and an opposite latching. head end; means pivotally attaching said attachment end portion of said finger to said cylinder with freedom for limited piv'- otal motion in a radial' plane relative tothe longitudinal axis of said cylinder, said attachment means including a projection attached to and extending laterally from said attachment end portion of said finger and forming afirst laterally off-set shoulder facing said latching head end of said finger; a projection attached to and extending laterally from said cylinder and forming a second shoulder facing opposite to saidk first-mentioned shoulder, said shoulders being positioned in mutual contact whereby move,- ment of said finger longitudinally in said cylinder in a direction toward its said latching head end is restrained; resilient meansacting' between said cylinder and said finger applying force longitudinally to said attachment end` portion of said finger at a point oli-set laterally in a direction opposite to the ofi-set of said first shoulder, whereby said finger is biased pivotally about a center formed at a point of mutual contact betweensaid firstand second shoulders and in a direction' toward one limit of said 'pivotal motion; a laterally-extending head formed on the said latching head end of said finger; and a latch recess means formed behind a laterally-extending' projection carried by said piston means, said laterally-extending head and said projection being positioned for abutment upon axial movement of said piston means toward said latching finger in said cylinder, saidlatching head and said projection being formed for lateral, camming engagement with each other upon occurrence of such abutment where.- by upon continued axial movement of said piston means relative to said cylinder to a' predetermined latchingposition therein, the said latching finger is pivotally cammed in opposition to said bias to slide over said projection and then be opposit'ely, pivotally moved by said bias into latching engagement within said latch recess.

l2. In a hydraulic actuatorhaving a cylinder and a piston means reciprocable axially therein, means for locking said piston means immovable at a predetermined axial position in said cylinder comprising: a plurality of separate, parallel, 1ongitudinally-extending, circumferentially spaced-apart latching fingers in said cylinder, said fingers each being pivotally attached at adjacent attachment ends thereof to the cylinder, with freedom for limited pivotal motion in a radial plane with respect to the longitudinal axis of said cylinder; resilient means biasing said fingers to one limit of such pivotal motion; a laterally-extending latching head formed on each of said lingers adjacent the end thereof opposite to said attachment ends; an annular, outwardly extending fiange carried on said piston means and positioned for endwise abutment with said latching heads upon axial movement of said piston means toward said latching fingers in said cylinder, said latching head and said flange being formed such that upon such abutment and continued axial movement of said piston means relative to said cylinder to a predetermined latching position therein the said latching fingers are cammed pivotally in opposition to said bias to permit the said latching heads to slide over the said fiange and then pivotally move inwardly under the force of said bias to latching engagement therewith.

13. In a hydraulic actuator having a cylinder and a piston means reciprocable axially therein, means for locking said piston means immovable at a predetermined axial position in said cylinder comprising: a plurality of separate, parallel, longitudinally-extending, circumferentially spaced-apart latching fingers in said cylinder, said fingers each being pivotally attached at adjacent attachment ends thereof to the cylinder with freedom for limited, outward, pivotal motion in a radial plane with respect to the longitudinal axis of said cylinder; resilient means biasing said fingers against such outward pivotal motion; a laterally inwardly extending latching head formed on each of said fingers adjacent the end thereof opposite to said attachment ends; an annular, outwardly extending ange carried on said piston means and positioned for endwise abutment with said latching heads upon axial movement of said piston means toward said latching fingers in said cylinder, said latching head and said liange being formed such that upon such abutment and continued axial movement of said piston means relative to said cylinder to a predetermined latching position therein the said latching fingers are cammed pivotally outwardly in opposition to said bias to permit the said latching heads to slide over the said liange and then pivotally move inwardly under the force of said bias to latching engagement therewith.

14. In a hydraulic actuator having a cylinder and a piston means reciprocable axially therein and having locking means for locking said piston means immovable at a predetermined axial position in such cylinder, a latching linger for said locking means comprising: an elongated body having a cylinder attachment end and an opposite latching head end, said attachment end being generally hook-shaped with a laterally off-set shoulder facing the latching head end thereof, adapted to be supported against an oppositely facing supporting shoulder, land a longitudinally extending projection laterally olf-set in a direction opposite to that of said shoulder; and a laterally projecting head adjacent the latch head end of said body extending laterally in the same direction relative to the axis of said body as said shoulder, whereby upon application of force longitudinally against said longitudinally extending projection with resultant reactive force against said shoulder, said latching linger will be urged to pivot, about a point of contact between said shoulder, in the direction in which said head laterally projects.

References Cited in the le of this patent UNITED STATES PATENTS 2,297,902 Levy Oct. 6, 1942 2,702,024 Harold Feb. 15, 1955 2,841,123 Conway July l, 1958 3,003,473 Ottoson Oct. 10, 1961 

1. IN COMBINATION: A CYLINDER; A PISTON AND PISTON ROD RECIPROCABLE AXIALLY IN SAID CYLINDER, SAID PISTON BEING AXIALLY SLIDABLE WITHIN SAID CYLINDER AND MOUNTED ON SAID ROD WITH FREEDOM FOR LIMITED AXIAL SLIDING MOVEMENT RELATIVE THERETO; MEANS FOR ADMITTING FLUID PRESSURE TO AN END OF SAID CYLINDER TO MOVE THE PISTON AND THEREBY MOVE THE ROD AXIALLY IN SAID CYLINDER; LATCHING MEANS ANCHORED IN THE CYLINDER, ENAGAGEABLE WITH THE ROD WHEN SAID ROD IS THUS MOVED TO A PREDETERMINED AXIAL POSITION IN SAID CYLINDER, TO HOLD SAID ROD AGAINST AXIAL MOVEMENT RELATIVE TO SAID CYLINDER; ANNULAR LOCKING MEANS COAXIALLY MOUNTED ON SAID ROD WITH FREEDOM FOR LIMITED AXIAL SLIDING MOVEMENT THEREON RELATIVE TO SAID PISTON AND ROD, FOR LOCKING WHEN IN A FIRST AXIAL POSITION RELATIVE TO SAID ROD, THE LATCHING MEANS IN SUCH ENGAGEMENT WITH SAID ROD; RESILIIENT MEANS URGING SAID LOCKING MEANS INTO SAID FIRST POSITION AND URGING SAID PISTON INTO A PREDETERMINED AXIAL POSITION 